Gear pump



Oct. 9, 1928. 1,686,867

L. o. KUHN GEAR PUMP Filed Nov. 1926 2 Sheets-Sheet 1 as v [/v VEN TOR lib A5 0. KuH/v ITTORNEHS Patented Oct. 9, 1928.

UNITED STATES PATENT OFFICE;

' ewis 0. 2mm, or us, mnmnsora om roim Application filed November 8, 1926. Serial No 147,046.

This invention relates to improvements in gear pumps, and has for objects to provide a pump of the rotary gear type suitable for general use, and of simple and durable const'ruction, so designed that all wearing parts are removable and replaceable and easily renewable at moderate cost, without disconnecting the pump body or cylinder from the pipe line, in whlch it is connected.

Another object of the invention is toprovide gears constructed so as to prevent loss of power due to squeeze-points this object being accomplished by providing radially disposed depressions at each side of each tooth, arranged to lie crosswise of and at each side of the pitch line.

.In designing a low-cost rotary gear.type of pump, it is necessary that self-driving gears should be used so that external drive liquid in a. radial direction. .lDuring such a period,the velocity of the liquid must be momentarily increased to permit the rotation of the. ears to continue. The velocity of the liqui can be increased only by increasing the pressure, hence fluctuatlng pressures. It is this fluctuation of pressure within the pump which causes pulsation of flow, variation of torque in the shafts, and

. general loss of eiiiciency. Squeeze-points also cause erosion and therefore rapid wear, due to the cutting action on the metal 'by ejection of liquid at high velocity from the pockets or traps, at a pressure'much higher than the normal discharge pressure. 7

There are virtually two general classes of gears which can be designed for use in rotary pumps, (1) gears which will drive each other, and (2) gears which will not drive each other. Moreover, gears for the use in rotary pumps may be further divided/ into classes comprising (1) gears which in meshing will pocketor trap liquid to form squeeze-points, and (2) gears which will not ocket or, trap liquid. Gears or rotors of t e latter classes must ordinarily have external driving or timing gears keyed to their shafts. Some makers of those gear pumps that fall in the first class, also use ilot gears, but with the object of relieving rivmg strains and consequent wear oil of thepump gears within the pump, and not for the purpose of synchronizingthe pumpmg gears proper.

The features of the invention include all details ofmonstruction, both of the pump and of the gears, per se, and their operative relations.

Other objects, certain advantagps, and

other features of theinvention w be set. forth in the description of the drawings,

forming. a part of this application and in said drawings,

Figure l represents a vertical longitudinal I section;

F igure 2 is a vertical transverse section on the line 2-2 of Figure 1;

V Figure 3 is a sectional elevation of the cylinder liner, providin av gear chamber, and gridlike intake and ischarge orifice;

Figure 4 is an inner face view of one of the closure and wearing plates; Figure 5 is a detail sectional view I showing the gear construction, and

' Figures 6 and 7 are respectively a section 3 and an end view, showing the gear tooth construction.

In the drawings, numeral 1 designates the main pump casing or cylinder providing a smooth bore portion 2. The casing as a casting, is flanged as at 3 at opposite sides, and is provided with abase portion 4 reinforced as by integral ribs. The base is bored as at 6 for the reception ofbolts 7 which in this instance secure the foot or baseforming angled castings 8, (see Figure 2). The outer faces of the fianges 3, are coplanar with the outer vertical annular faces of the cylinder, (see Figure 2). The use of base-forming castings 8 provides a knockdown construction, convenient in shipping.-

The casting or cylinder is provided with integral tubular extensions 10 and 11 respectively as discharge and suction conduits, depending upon the direction in which the pump drive shaft is rotated. These extensions are diametrically arranged as 'shownin Figure 1 and are preferably terminally flanged, foriconnection with correspondingly flanged supply and delivery conduits'designated 12 and 13. If desired, these. extensions may be threaded, instead of flan ed.

, 'Removably fitted within the cylinder is ill what I term a cylinder-liner, generally indicated as 15. This lner has the general configuration of a cylinder, and the central pump gear chamber is machined as at 16 and 17, conformably to the size and arrangement of the pump gears. The intersecting bores provided for this purpose are slightly larger in dameter than the outside diameter of the gears, and the width of the liner is slightly greater than the width of thegears. The axial and radial clearance for the gears can be varied and must be varied in proportion to the viscosity of the liquid to be pumped if the best results are to be secured. Liquid enters the gear chamber through'grids, one of these grids being supplied at each side, and each in this instance being composed of two bars 18, vertically arranged, and perpendcular to the axes of the gears, and providing' three inlet spaces or openings 19, which in this instance are vertically elongated. It will be noted that the grids lie inwardly from the periphery of the liner, (see F..gure 1). On each side of the cylinder liner are shown openings 20 for the reception of dowel pins 21, which are provided for determiningthe correct position of the liner in the original assembly of the pump, and for maintaining the liner in proper position.

' The cylinder liner is a comparatively sinjiple casting and the final machinlng operations 4 are simple. This casting can be easily' reltially' 'the placed when worn. The grille-like center construction (see Figures 1 and .3) serves as a screen to keeplarge forei bodies from reaching the gears, and the grilles also facilitate the removal of the worn .rcasting'from the cylinder, inasmuch as they may be bro ken, if the casting is stuck or corroded within the cylinder, thus permitting removal in two pieces.

An added advantage of this design of renewable cylinder liner, is that the liner may made of more costly metal than, the body 'ofthe pump where such metal is desirable, without prohibitive cost. Metals which are nore'res stant to abrasion, erosion or corrosion, than iron can be used without excessive cost. Therefoi e, it will be seen that this chambered removable cylinder liner is an important feature. 1'

The liner is held in position against axialv movement, by .what may be designated, a pair of closure plates 30, 31. These plates are each provided with a pair of bores'32 and33,

as bearingsagThe form of plates is substanplatewhichvhavesthe bores therein, are in the form of lateral extensions, to give a long ent. of the bores is ail-bearing has 1 indicated at 34,

r and a sho flder 35. =s -pmv1aed at the inner end of each to abuttingly receive and revent inward translation of 'the bushing. ese formed of bronze or and those portions of each other suitable metal and are preferably pressed into place. The plates are-sealingly secured by bolts 36, and act to close the op posite sides of the annular base member;

a The gears are designated 40, 41. One of the gears, preferably the upper, is' provided with elongated integral shaft extensions re spectively designated 42, 43 which pass through and are journaled in the bushings 34. In this instance,the shaft extensions 42 form the drive shaft for the gear, and is suitably tapered reduced and threaded for connection with a suitable prime .driver, not shown; The extensions 42 and 43 are of course axially aligned and each extends to a point outside of the pump casing. In this in stance, the lower gear 41 is provided with a similar pair of shaft extensions 45, 46 which however, do not extend beyond the pump casing, as in the case of the extensions of the upper gear.

Iteservoir-foiming covers 50, each provided with astufiing box 52, are suitably se-- cured laterally of and flatly against the bearing-forming extensions of the side plates 30, 31. The shafts 42, 43 extend through respective stufling boxes 52. It will be noted that the ends of the shafts 45, 46 of the lower gear receive oil from the reservoir thus formed. The reservoirs are fille through sutable openings 54. I

Another important feature is the provision of wear-plates 60. These plates are for receiving thrust of the end faces of the gears, and may be reversed when worn on one side. The object of the plates is to provide means for maintaining the p'roper axial clearance between the ends' of the gears and the end plates 30'. They are pot made adjustablejor the reason that it is cheaper and easier to 'renew them,

" and then, too, the correct needed amount of adjustment would be diflicult to ascertain. Like the cylinder liner the wear plates'may be made of an desired metal, at'reasonable cost, because t e same can be made thin and light; The plates are simple and are intended to be symmetrical so that no mistake can be made in re lacement. Openings 63 are traversed b t e g'ear shafts, see Fig ures 2 and 4; bymeans of through openings pinsalso engaging openings 20 and 25 respectively in the liner 15 and end plates 30.

The simplicity of these wear'plates fiO, is

the dowel pins 20 passing 61 in the plates, the same orrect alignment is assured,

scovered for relieving the squeeze-points, i -means of relief grooves cut in the teeth, j

p'pssible only because of the method I have b making lateral ports unnecessary. a Itis understood that the width of the gears is almost equal to the width of the cylinder liner, and that the diameter of the gears is almost equal tothe diameter of r.-" bores, which form the spective cylinder liner iseneeaeer and if the pump is to continue to operate satisfactorily over a-long period of time, the lateral or axial and the radial clearance just mentioned must be kept constant. This can be done only by providing means for renewin the cylinder walls, the inner surfaces 0 the flanking end plates, and the ing squeeze-points, I will periphery of the rotors or gears. The cylinder liner and the plates herein. provide means for renewing these surfaces easily, quickly and cheaply.

The gears 40, 41, the detailed construction of which is shown in Figure 5, may have any suitable form of tooth. The gears may be of steel forged integral with the shafts, or maybe made separately and of metal different from the shaft metal. The gear teeth may be of any form and in cases where low first costs is not of primary importance, and where external pilot gears are considered necessary, it is intended that such constructions are not prohibitive in this invention. V Y

Before proceeding to describe in detail the construction of the ears for preventi iriefly describe the principle on which this pump and all other rotary gear types of pumps operate. The direction of rotation of the gears is indicated in Figure 5. j 1

Starting with a dry or empty pump, the rotation of the gears in the directionin'dicated meshes the gear'teeth' and squeezes out the air orignally contained in the spaces between the, teeth As the teeth unmesh on the other side, they tend to create acondition of vacuum in the spaces which formerly were filled with air but "which air was ex pelled on the discharge side. These vacuum spaces are immediately filled with air contained in the suction side of the pump. Each tooth space carries air from the suction side of the pump aroundto'the dis-. charge side] and the air-filled spaces are emptied into the-discharge line, thereby exhaustingthe air from the suction line, which of course must be air-ti ht and which must extend beneath the'snr ace of the liquid it is desired to pump. As the air is drawn-out of the suction line, a condition of'vacuum is produced, "or, in. other words, the normal atmospheric pressure is removed from the.

surface of the liquid inpthe suction line,

-' and "the atmospheric pressure on the surface of the li uid outside the suction line forces the liqui towards the pump. When the liquid reaches the pump, the action of the pump on the liquid is the same as it was on the air and the tooth spaces or kets are filled with liquid on the suction side and expelled by the meshing teeth on thedischarge side. Rotary to multi-cyhn the tooth spaces correspond to t e cylinders and the teeth correspond to the (plungers and which plungers work intoa'n out of the cylinders with a rotary rolling action instead of with a straight rgciprocatin motion. The contacts between the teet of the two gears serve to separate the discharge from the suction side ofthe pump, and thereby take the place of the suction and discharge valves which must be present in plunger pumps. I

In order to eliminate the ueeze-points, and the erosive and other detrimental effects caused thereby, and due to pocketing of liquid bythe teeth, I providede ressions inthe teeth of one of the gears, an arrange dgear pumps may be likened the depressions on both working faces of pitch line. By experimenting, l have found that the best location, of and arms ement for the relief grooves is substantia y that shown in the drawings.

By an inspection of Figure 5-and referring to the relation of teeth a, b and c, it will be noted that the opposingly related relief grooves 65, respectively of the teeth '6 and 0, "respectively engage the working faces of the tooth on, at, anda't a point above or at the outer side of the pitch line. It

will also be noted that since one of the grooves lies symmetrically at opposite sides of the pitch line, relief will be ad through er plunger pumpls in which one or the other of the depressions durlng.

the while period that'the working faces are in contact.

By reference to Figure 5, it will be seenthat at certain oints in the rotation of. the

gears} the liquid in one pocket or groove I would be trapped, and would have to be expelled in a very small fraction of time through a very small orifice, unless the relief grooves were resent to permit relatively free egress. o the liquid.

4 The relief depressions have been as trapped in the tooth spaces with reference to the dischargeside, but they also perform a very importantduty onfthe suction side. By reference to Figure 5, it be'seen described. providing radial outlet-for that liquid that the unmeshing of the'teeth tends to The) effect of creating a condition of :form a 'vucuum in the tooth spaces, before. the liquid can enter in a radial direction, '1 except through the frlief depressio1 ns,.--1 2h vacuum in'the spaces prior to the opening of the inlet ports tends to cause noisy operation, and this I have elminated by provlde ingthe depressions. 1

I claim as my invention:

1. A device of the class described comprising a pump base having a main bore, and inlet and outlet conduits communicatingwith the bore, said conduits being horizontally anddiametrically related, a liner element as a casting providing a twin-gear chamber, the opposite vertical walls of said chamber, being vertically slotted to provide gridlike intake and discharge orifices arranged for communication with respective conduits, and meshed gears within said chamber, each gear having shafts axially aligned at opposite sides and journaled in said base and bearing plates closing the bore and enclosing the liner, and receiving the shafts and dowels connecting said bearing lates with said liner to permit removal of are bearing plates in an axial direction.

2. A gear having its teeth provided with depressions, said depressions being formed in both working faces of each tooth, and extending at both sides of the pitch line.

3. A gear having its teeth provided with concave depressions, said depressions being formed in both working faces of each tooth, and extending at both sides of the pitch line.

4:. A gear having its teeth provided with depressions, said depressions being formed in both working faces of each tooth, and bein extended at both sides of the pitch line, su stantially symmetrically, the length of said depression being less than, the length of the teeth;

5. A gear having each of its teeth provided with depressions, said depressions being formed in both working faces of the tooth and being extended at both sides of the circular pitch line, said depressions being of less radial length than the de th of the tooth. and extending symmetrica y at both sides of said circular pitch line but not extending the full length of the tooth,

6. A pump base having a bore, and substantially diametrically related inlet and outlet passa es communicating with the bore, a liner fitted in said bore and having a gear chamber, the walls of the linerbein formed to provide two series of spaced grid bars arranged to establish communication respectively between the inlet and outlet pas sages across the gear chamber, the bars being so constructed as to permit their fracture in a manner to permit the liner to be removed in sections. a

7. A pump comprising a base having a bore and inlet and outlet conduits communi eating with the bore at op osite sides, a liner element fitted within the ore and havin a gear chamber, those walls of the chamber opposed to the inlet and outlet conduits each formed to provide a series of spaced grid bars establishing communication with the chamber and said ,assages, meshed gears within the chamber aving shafts extending from opposite sides, and bearing plates closceiving the gear shafts.

ing the bore at opposite sides and secured'to' the base and having elongated bearings 're- 8. A pump comprising a base having a bore and inlet and outlet conduits communicating with the bore at opposite sides, a liner element fitted within the bore and having a gear chamber, those walls of the chamber opposed to the inlet and outlet conduits each formed to provide-a series of spaced grids establishing communication with the chamber and said passages, meshed gears .ithill the chamber having shafts extending from opposite sides and bearing plates closing the bore at opposite sides and secured to the base and having elongated bearings receiving the gears afts, and dowels connecting thebearing p ates with theliner.

9. A pump comprising-an bore and inlet: and outlet conduits OOIIHIIIIDI- cating with'the bore at opposite sides, a liner element fitted within the bore and havin a gear chamber, those walls of the cham r opposed to the inlet and outlet conduits each formed to provide a seriesof spaced 'ds establishing communication with the c amber and said passages, meshed gears within the chamber having shafts extendin from opposite sides and bearing plates closing the bore at opposite sides and secured to the base and having elongated bearings receiving the ear shafts, and dowels connecting the bearing plates with the liner, and wear plates interposed betweenthe liner and the bearing, the dowels and gear shafts also passing through said wear plates.

10'. A pump base having a and inlet passages at opposite sides of the bore and communicating therewith, a liner fitted within the bore and having a gear chamber having gridded walls establishing communication between the gear chamber and inlet and outlet passages, and opposed to respective passages, bearing elements. arranged at opposite sides to close the bore and enclose the grid, and gears within the gear chamber having shafts rotatable in said bearing elements.

11. A pump base having a bore and outlet and inlet passages at opposite sides of the bore and communicating therewith, a. liner fitted within and of less area than the bore and having a gear chamber having gridded walls establishing communication between the gear chamber and inlet and outlet passa es, bearing elements arranged at opposite sides to close the bore and enclose the grid, gears within the ear chamber having shafts rotatable in said caring elements, and dowels securing said liner to said bearing elements, the arrangement being such that the dowels are released when the bearing ele' ments are moved in an axial direction.

12. A pump comprising a base having a bore extending -therethrough, and inlet and base having a bore and outlet llu outlet passages leading into the here from opposite sides, a liner fitted within and of less area than the bore and substantially diametrically related to the bore axis in a direction substantiall at right angles to the axes of the outlet an inlet assages, and providing a gear chamber t e walls of the liner belng slotted to provide a set of grids at each opposite side of the chamber establishing communication between said passages and the ear chamber meshing gears m said eham r each having a shaft extending in opposite directions, bearing plates secured at op ite sides against the base and receiving t e shafts and said elements closing the bores, and enclosing the liner, and dowel pins connecting the liner to the bearing plates to secure the liner against displacement.

13. A pump comprising a base'having a bore extending therethrough, and inlet and outlet passages leading into the here from opposite sides, a liner fitted within the bore and roviding a ar chamber, the walls of the er being otted to provide a set of grids at each opposite side of the chamber substantially perpendicular to, the axes of the outlet and inlet passages and establishin communication between said passages an the ear chamber, meshing gears in said cham er each having a shaft extending in opposite directions, bearin plates secured at o posite sides against the ass and receiving t e shafts and said elements closing the bores, and enclosing the liner, and dowel pins connecting the liner to the'bearing plates to secure the liner against displacement.

14. A pump base having a bore, and substantially diametrically related inlet and outlet passages communicatin with the bore, a liner fitted in said bore and having a gear chamber, the walls of the liner being formed to provide two series of spaced grid bars opposingly arranged to establish communication respectively between .the inlet and outlet passages across the gear chamber, the bars being so constructed as to be fractured in the manner to permit a liner to be removed in sections, the area of contact between the liner and bore being substantially less' than the surface area of the bore and aid liner extending from end to end of the In witness whereof, I have hereunto set n'iy hand this 4th day of November, 1926.

LEWIS o. KUHK. 

